Before going into the tower, surf East across the water. More tall grass is across the moat, along with a Carbos. Now enter Dragonspiral Tower.

First Floor

The first floor is a straight shot to the second.

Second Floor

The second floor has a few collapsed columns around the room. You can walk up and across the columns in the back like a bridge. This bridge will connect to the West side of the room. An Elixir can be found near the collapsed columns in the back as well.

Pushing the boulder to the West will allow you to reach the same area. A bit South is an Ultra Ball on half a column.

Third Floor

The third floor is sort of a maze. Jump from platform to platform using the ramps. Follow these instructions to pick up the two items and reach the exit:

Jump down to where the three ramps are. First, use the middle ramp to jump three platforms over. A Shiny Stone can be found on the last platform.

Jump across the ramps up, up, right, and right to reach a platform where a Protein is located.

Return back to the starting position and down to the three ramps once more. This time, take the bottom ramp until you reach the curved staircase at the far side of the room. Take the stairs up to the fourth floor.

Fourth Floor

Fifth Floor

The fifth floor is another maze area. This particular area is a bit confusing to get through because the camera moves with you. Try to follow these instructions:

From the entrance, head right until you find a bridge. Cross the bridge to the next ring inward. Walk left until you reach another bridge to the next ring inward, and pick up TM02 - Dragon Claw on the other side.

Jump the ledge to the right of the TM. Walk right along the ring past the first bridge, then cross the next two bridges two rings outward. Head left to find an HP Up at a dead end.

Return across the two bridges until you reach the ring with the ledge you jumped after obtaining TM02. This time, take the other bridge to the next ring inward. This ring is the center pillar. Jump the ledge in the center pillar, then cross the bridge to the next ring outward. Head left, cross the bring to the next outer ring, then head right until you reach a Max Revive.

Walk left until you reach a bridge to the final ring outward. Head left up the stairs to the next floor.

Sixth Floor

The sixth floor is another simple path to the next floor. Pick up the Comet Shard along the way.

Seventh Floor

Walk to the middle of the seventh floor. The game will ask if you want to use the Dark Stone or Light Stone. Choose "yes" to release Zekrom (Black 2) or Reshiram (White 2). As noted at N's Castle, it depends on the version you're playing. After a short cut scene, you will be able to battle and capture the legendary Pokemon. Make sure to save your game before attempting to do so! Try using Ultra Balls and Timer Balls. Save your Master Ball for the next Legendary Pokemon.

Legendary Pokemon Zekrom

Make sure you catch this Legendary Pokemon! If you don't, you won't be able to create Black Kyurem when you catch Kyurem later on.

After capturing the Legendary Dragon Pokemon, N will come by for a bit of a chat. When he's done, use your Dowsing Machine to find a hidden Comet Shard in the North East part of the room. Now that you have this legendary dragon, it's time to catch Kyurem at Giant Chasm.

Another thing to do is meet N at the Ferris Wheel in Nimbasa City on Friday. After riding the wheel with him, return to N's Castle to battle him in an extremely tough 6 on 6 battle. His team will change depending on the season.